Characterisation of biotinylated liposomes for in vivo targeting applications.

Liposomes containing monosialoganglioside (GM1) or polyethylene glycol (PEG) lipid derivatives have prolonged circulation in the blood. This favours liposome extravasation to tumour sites. In this report it is shown that inclusion of GM1, PEG550-DPPE or PEG2000-DPPE in liposomes containing biotin-DPPE significantly diminished the ability of vesicles to bind to streptavidin in vitro. Steric inhibition due to the bulky head group of these lipids was least for biotin-DPPE liposomes containing GM1. Biodistribution studies in C26 tumour-bearing mice showed that GM1-liposomes containing small amounts of biotin-DPPE have long circulation life-times in the blood. Using fluorescent microscopic techniques, liposomes containing both GM1 and biotin-DPPE were detected within extra-vascular spaces in tumours. In addition it was shown that biotin-DPPE in GM1-liposomes bound streptavidin in situ. These results suggest that GM1-liposomes containing biotin-DPPE have potential use as diagnostic or therapeutic reagents in pre-targeting applications dependent on the high-affinity interaction of biotin with streptavidin.

Meldola Blue for the cytochemical demonstration of leukocyte dehydrogenases.

The new electron carrier Meldola Blue was employed in the cytochemical demonstration of succinate, lactate, and glucose-6-phosphate dehydrogenases in leukocytes. A significant increase in dehydrogenase activity, with better localization and less diffusion of the reaction product, was observed when compared to enzyme reactivity carried out without Meldola Blue. Meldola Blue can facilitate the demonstration of both bound and soluble leukocyte dehydrogenases. Current methods which could yield better visualization of leukocyte dehydrogenases, particularly succinate, lactate, and glucose-6-phosphate dehydrogenases in neutrophils, suggest excellent use can be made of Meldola Blue in the clinical laboratory. Reliable histochemical determination of these enzymes can aid in differentiating younger from older neutrophils. In addition, glucose-6-phosphate dehydrogenase might be used in conjunction with the nitroblue tetrazolium (NBT) test in separating persons with bacterial infections from those with nonbacterial illness. Furthermore, histochemical visualization of this enzyme may also prove beneficial in identifying glucose-6-phosphate dehydrogenase-deficient individuals.

Nonspecific esterase activity in plastic-embedded tissues using Meldola Blue.

A method for the demonstration of nonspecific esterase activity in plastic-embedded tissues using Meldola Blue is described. Although Meldola Blue does not function as an electron carrier in this method, it may account for the short incubation time and excellent localization of the reaction product. Use of Meldola Blue is an advancement in the demonstration of enzyme activity in plastic sections.

A histochemical study of the microvasculature in the left and right cardiac ventricles of the dog.

Subepicardial and subendocardial arteries and arterioles in both the left and right normal canine ventricle were examined histochemically to determine their metabolic profiles. Aerobic metabolic capacity was assessed by determining the reactivities of the enzymes cytochrome oxidase, succinate dehydrogenase and NAD-isocitrate dehydrogenase. Glucose-6-phosphate dehydrogenase was examined to assess activity of the hexose-monophosphate-shunt. The substrate glycogen was determined as an evaluation of anaerobic metabolic capacity, while the amounts of deoxyribonucleic and ribonucleic acid were assessed as an indication of protein synthesis. Results of the present investigation indicate that despite known hemodynamic differences, the metabolic profile of the coronary vasculature is similar in all regions of ventricular myocardium. Reactivities of the enzymes succinate and NAD-isocitrate dehydrogenase and cytochrome oxidase are greater in smooth muscle of arterioles than in arteries. This suggests that arteriolar smooth muscle has a higher capacity for aerobic metabolism than does arterial smooth muscle. The greater reactivity of glycogen in arterial, than in arteriolar smooth muscle, suggests that arterial muscle is more adapted for anaerobic metabolism. Deoxyribonucleic and ribonucleic acids demonstrate a low reactivity in both arteries and arterioles from all regions of ventricular myocardium which conforms to the opinion that under normal conditions, coronary vasculature is quite stable with little cell proliferation. Glucose-6-phosphate dehydrogenase shows little reactivity in all myocardial vessels with implies a low capacity for nucleic acid and protein synthesis.